I have used it for Mturk survey completion code. I found some codes are drawn several time.

question('RG01'); // You may as well drag the RG01 into the page (above)
// Stop right now, if no more codes are available
if (value('RG01_CP') > 0) {
text('quotafull');
buttonHide();
pageStop();
}
// EITHER Prepare placeholder %code%
// and use this placeholder in some text element below the PHP code
replace('%code%', 'RG01', 'response');
// OR display the code immediately
html('<p>Your Mturk Survey Completion Codes is: <strong>'.value('RG01', 'label').'</strong>.</p>');